What was found
L PACK WAS SURGING IN THE CLIMB OUT. ECS PAGE SHOWED L ENG BLEED MOMENTARILY OPENING AND CLOSING ALONG WITH THE GREEN LINE TO THE L PACK MOMENTARILY OFF. PRESSURE CONTROLLER WAS SWAPPED TO PRESS CONT 2 AND INDUCED DIFF PRESS WARNING MESSAGE. INITIATED DECENT TO 10,000, REGAINED PRESSURIZATION AND DIVERTED. (FLIGHT 3831 - FILED CLOSED)PERFORMED OPS CHECKS OF THE CABIN PRESSURISATION SYSTEM IN REFERENCE TO AMM 21-31-00-910-801. OPS CHECK GOOD. SEE AML 1480654 AND AML 1480658 FOR FURTHER AIR CONDITIONING AND BLEED SYSTEMS OPS CHECKS